Dual-Salt Localized High-Concentration Electrolyte for Long Cycle Life Silicon-Based Lithium-Ion Batteries

Silicon-based materials are considered the most promising anodes for next-generation lithium-ion batteries (LIBs) owing to their high specific capacity. However, poor interfacial stability due to enormous volume changes severely restricts their mass application in LIBs. Here, we design a fluoroethylene carbonate (FEC)-containing dual-salt (LiFSI-LiPF6) ether-based localized high-concentration electrolyte (D-LHCE-F) for enhancing the interfacial stability of silicon-based electrodes. It is revealed that the dominating LiFSI salt of superior chemical and thermal stability prevents the formation of corrosive HF, while the addition of FEC improves the interface stability by promoting the formation of protective LiF-rich SEI and increasing the flexibility of the interface. This robust and flexible SEI layer can adapt to substantial variations in the volume of silicon electrodes while preserving the integrity of the interface. The SiOx/C electrode using the unique D-LHCE-F retains up to 78.5% of its initial capacity after 500 cycles at 0.5C, well surpassing that of the control electrolyte (3.4% capacity retention). More notably, the cycle life of the SiOx/C||NCM90 (LiNi0.9Co0.05Mn0.05O2) full batteries is effectively enhanced thanks to the stabilized electrode/electrolyte interfaces. The key findings of this work offer crucial knowledge for rationally designing electrolyte chemistry to enable the practical application of high-energy-density LIBs adopting silicon-based anodes.